// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2008 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#include "trackball.h"
#include "camera.h"

using namespace Eigen;

void
Trackball::track(const Vector2i& point2D)
{
	if (mpCamera == 0)
		return;
	Vector3f newPoint3D;
	bool newPointOk = mapToSphere(point2D, newPoint3D);

	if (mLastPointOk && newPointOk) {
		Vector3f axis = mLastPoint3D.cross(newPoint3D).normalized();
		float cos_angle = mLastPoint3D.dot(newPoint3D);
		if (std::abs(cos_angle) < 1.0) {
			float angle = 2. * acos(cos_angle);
			if (mMode == Around)
				mpCamera->rotateAroundTarget(Quaternionf(AngleAxisf(angle, axis)));
			else
				mpCamera->localRotate(Quaternionf(AngleAxisf(-angle, axis)));
		}
	}

	mLastPoint3D = newPoint3D;
	mLastPointOk = newPointOk;
}

bool
Trackball::mapToSphere(const Vector2i& p2, Vector3f& v3)
{
	if ((p2.x() >= 0) && (p2.x() <= int(mpCamera->vpWidth())) && (p2.y() >= 0) &&
		(p2.y() <= int(mpCamera->vpHeight()))) {
		double x = (double)(p2.x() - 0.5 * mpCamera->vpWidth()) / (double)mpCamera->vpWidth();
		double y = (double)(0.5 * mpCamera->vpHeight() - p2.y()) / (double)mpCamera->vpHeight();
		double sinx = sin(M_PI * x * 0.5);
		double siny = sin(M_PI * y * 0.5);
		double sinx2siny2 = sinx * sinx + siny * siny;

		v3.x() = sinx;
		v3.y() = siny;
		v3.z() = sinx2siny2 < 1.0 ? sqrt(1.0 - sinx2siny2) : 0.0;

		return true;
	} else
		return false;
}
